What are the recommended exercise type, duration, intensity, and safety precautions for adults or adolescents with prediabetes or type 2 diabetes?

Role of Physical Activities in Prediabetes and Diabetes

Core Exercise Prescription

Adults with prediabetes or type 2 diabetes must perform at least 150 minutes per week of moderate-to-vigorous aerobic activity spread over at least 3 days, with no more than 2 consecutive days without exercise, combined with resistance training 2–3 times weekly on nonconsecutive days. 1, 2

Aerobic Exercise Requirements

• Minimum weekly target: 150 minutes of moderate-to-vigorous intensity aerobic activity distributed across at least 3 days 1
• Critical timing rule: Never allow more than 2 consecutive days between exercise sessions, as the acute insulin-sensitizing effect wanes within 48–72 hours 1, 2
• Session duration: Each aerobic bout must last at least 10 minutes, progressing toward approximately 30 minutes per session 1, 2
• Acceptable activities: Walking, cycling, swimming, dancing, yoga, housework, and gardening all count toward aerobic goals 1, 2
• Alternative for fit individuals: Younger, more physically fit adults can substitute 75 minutes per week of vigorous-intensity or interval training (e.g., running at 6 mph for 25 minutes) 1

The 2-day gap rule is non-negotiable because insulin resistance returns rapidly after 48–72 hours without activity. 2 Higher exercise intensities (40–60% VO₂max) produce greater reductions in HbA1c and cardiorespiratory fitness improvements compared to lower intensities. 2

Resistance Training Requirements

• Frequency: 2–3 sessions per week on nonconsecutive days to allow 48 hours for muscle recovery 1, 2
• Exercise selection: Target major muscle groups including chest press, rows, squats, leg press, shoulder press, lat pulldown, leg curls, leg extensions, and core exercises 2
• Volume: At least 1 set of each exercise with 10–15 repetitions per set 2
• Intensity: Any intensity improves strength, balance, and glycemic control—even light resistance training benefits those unable to tolerate heavy loads 1, 2

Resistance training is particularly important for patients on GLP-1 receptor agonists or post-bariatric surgery to prevent sarcopenic obesity and maintain lean body mass during weight loss. 1

Breaking Sedentary Behavior

• Interrupt prolonged sitting every 30 minutes with brief standing, walking, or light activity 1, 2
• This provides independent glycemic benefits beyond structured exercise sessions 2
• Reducing sedentary time (computer work, television viewing) is as important as adding structured exercise for glycemic control 1, 2

Youth-Specific Recommendations

Children and adolescents with prediabetes or diabetes require 60 minutes daily of moderate-to-vigorous aerobic activity, plus muscle-strengthening and bone-strengthening activities at least 3 days per week. 1

• The daily 60-minute target for youth is higher than the adult weekly distribution because of developmental needs for bone and muscle growth 1
• Activities should include vigorous muscle-strengthening and bone-strengthening components at least 3 days weekly 1

Safety Precautions and Pre-Exercise Screening

Cardiovascular Assessment

• Routine cardiac stress testing is NOT recommended for asymptomatic individuals—a thorough history and risk assessment suffice 2
• Screen for uncontrolled hypertension, known coronary artery disease, and atypical chest symptoms before initiating exercise programs 2
• Autonomic neuropathy may alter cardiovascular responses to exercise and requires program modifications 2

Retinopathy Precautions

• Proliferative or severe non-proliferative retinopathy contraindicates vigorous activity due to risk of vitreous hemorrhage or retinal detachment 2
• Patients with advanced retinopathy should limit activities involving jarring, breath-holding, or head-down positions 2

Foot Complications

• History of ulcers or Charcot foot necessitates modified exercise selection and appropriate footwear 2
• Ensure proper footwear and daily foot inspection for individuals with peripheral neuropathy to prevent injury 2
• Non-weight-bearing activities (swimming, cycling) should be considered if peripheral neuropathy or active foot problems exist 2

Hypoglycemia Prevention (Insulin or Secretagogue Users)

• Check glucose before, during, and after exercise 2, 3
• If pre-exercise glucose is ≤90 mg/dL (5.0 mmol/L), ingest carbohydrates unless insulin dose can be reduced 2, 3
• Adjust medication timing and dosing around exercise sessions to avoid hypoglycemia 2, 3
• Post-exercise hypoglycemia can persist for several hours due to heightened insulin sensitivity 2
• Individuals using insulin pumps should consider lowering insulin dose during workout periods 2
• High-intensity activities may actually increase blood glucose when pre-exercise glucose is elevated 2
• In patients not treated with insulin or insulin secretagogues, hypoglycemia is uncommon and routine preventive measures are generally unnecessary 2

Expected Clinical Outcomes

Glycemic Control

• Structured exercise interventions of at least 8 weeks reduce HbA1c by an average of 0.66%, even without significant BMI change 1
• Exercise consistently improves insulin action regardless of weight loss 2
• A dose-response inverse relationship exists between physical activity frequency and HbA1c, BMI, hypertension, dyslipidemia, and diabetes complications 1

Cardiovascular and Mortality Benefits

• Moderate-to-high volumes of aerobic activity substantially lower cardiovascular and overall mortality risks in both type 1 and type 2 diabetes 1, 2
• Higher physical activity reduces mortality risk after a mean follow-up of 11.4 years in patients with and without chronic kidney disease 1
• Additional benefits include improvements in blood pressure, lipid profile (triglycerides, LDL), waist circumference, and overall well-being 2

Implementation Strategy

Progression for Previously Sedentary Individuals

• Initiate with short, low-intensity activity for previously sedentary individuals 2
• Gradually increase intensity and duration as tolerated 2
• Progress stepwise toward the target of ≥150 minutes per week 1, 2
• Medical monitoring may be indicated as exercise intensity escalates to ensure safety and evaluate effects on glucose management 1, 2

Common Pitfalls to Avoid

• Never allow more than 2 consecutive days without activity—this eliminates the acute insulin-sensitizing effect 1, 2
• Do not rely solely on structured exercise while ignoring sedentary time—breaking up sitting provides independent benefits 1, 2
• Avoid starting vigorous exercise without cardiovascular screening in patients with atypical symptoms or known coronary disease 2
• Do not overlook foot inspection and proper footwear in patients with neuropathy 2
• Ensure medication adjustment protocols are in place before exercise for insulin/secretagogue users 2, 3